Your card should still support Dx11's API, it just won't be able to perform many of the new Dx11 features. The Dx11 API is supposed to be downward compatible. You may even find you get better performance with the Dx11 API, as the new API was supposed to make some improvements in how it performs certain tasks.
Some of the things that won't work on your card when using Dx11 will be tessellation and Ambient occlusion.
Despite the fact that the GTX 200 series CUDA cores themselves are advanced enough to handle most of the requirements for DX11 (it's a little overkill for DX10 actually) it doesn't handle all the features and more importantly no tessellation. So no DX11 for you, but it's not too important right now. Visual improvements from DX10 to 11 are hard to notice during actual game play right now.
thanks for your comments, I like many games on the PC, this card actually buy some time by that of crysis, and now I am planning to buy the 2, I read something that is not as demanding as requirements first, not if you know something, I advise, stick with that card or it would be a new me?